UART and serial is ubiquitous, but there’s very few cheap, through-hole slave devices that use it. Without a serial device we only have 2 (3 with the 74HC595) protocols covered in the kit. Our (current) solution is to program the cheapest possible ATTINY with a little firmware that responds to serial commands.

Commands control PWM output to LED, measure with frequency probe

Terminal feedback, hidden messages, modes, etc

Logic Analyzer on repeating serial (or other) output

Why an ATTINY and not a PIC, MSP430, etc? The Bus Pirate can directly program most AVRs through AVRDude and there is an open/free IDE and compiler. We can include a short programming exercise in programming a chip without a bootloader. This might help someone revive and Arduino later too.